Process of dewaxing hydrocarbon oils



March 11, 1941. L D. .JoNEs PROCESS OF DEWAXING HYDROCARBON OILS Filed Dec. 2, 1938 5.3 A LQTCOU Coqlow Vdf Mdmniro INI/ENTOR- LEO D. l ONES moo@ LEGO@ BY (www OUA/M LMHOBVM X63 A TTORNE Y Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE Leo D. Jones, Philadelphia, Pa., assignor to The Sharples Corporation, Philadelphia, Pa., a corporation of Delaware Application December 2, 1938, Serial No. 243,560

12 Claims.

The present invention relates to the separation from each other of wax and lubricating oil contained in petroleum stocks. It pertains more particularly to an amplification of the procedure of my prior Patent 1,649,117, whereby the yield of dewaxed oil produced by the process of that patent may be materially increased and a wax of high melting point separately and economically obtained as a product of the process.

In the process of dewaxing described in the patent to P. T. Sharples, 1,351,265, the stock to be dewaxed is rst diluted with a sucient amount of a relatively low-boiling hydrocarbon solvent, such as naphtha, to render the oil phase, upon l5 subsequent chilling to precipitate wax, distinctly lighter than the precipitated wax. The diluted stock. containing both oil and wax, is thereafter chilled to a temperature below 0 F., in order to `precipitate, the wax from solution in the oil and diluent. The mixture of precipitated wax in the oil solution is thereafter passed continuously into a centrifugal to effect stratification of the Wax and separate discharge of the wax and diluted oil phases from the centrifugal rotor. In the process described in Sharples Patent 1,351,265, a carrier liquid which is immiscible with the oil and wax is employed to facilitate the flow of the wax phase through the centrifugal rotor and discharge of Wax from the rotor. This carrier liquid was originally introduced into the centriiugal rotor at a zone adjacent to the zone of introduction of oil and wax and fullled the important function of preventingr sticlrage of wax to parts of the rotor,.and reduction of friction in the wax discharge passages.

The process of Sharples Patent 1,351,265 went into extensive commercial use. A disadvantage of the process lay in the fact that the carrier liquid had to be chilled to as low a temperature as-that of the chilled oil solution and that difculty was sometimes encountered in removing Wax from the covers into which said wax was discharged from the centrifugal rotor and in effecting flow of this wax through the conduits into which it passed from such discharge covers. These dimculties in the process of Sharples Patent 1,351,265 were solved by an improvement invented by the present applicant. This improvement is described and claimed in the patent to Jones, 1,649,117. It consisted in feeding the carrier liquid to the upper end of the centrifugal rotor adjacent the point of discharge of wax from the rotor. By feeding carrier liquid adjacent the wax discharge, instead of to the zone of the rotor at which the oil and wax were introduced, the temperature of the carrier liquid had no effect on the wax separation in the rotor. It was then possible, by the application of this top feed principle, to use a heated carrier liquid and melt the discharging wax, thus facilitating the subsequent handling of the wax-carrier liquid mixture.

The present invention relates to a process of effecting further treatment of the wax phase discharged from the centrifugal rotor in accordance with the process of Patent 1,649,117. Wax discharged from the centrifugal separator in the operation of the process of Patent 1,649,117 contains a substantial quantity of entrained oil, the oil content of the wax varying between 20 and 50%. It is, of course, desirable to reclaim this entrained oil if this can be done economically. A particular object of the present invention has been to afford a process whereby the oil entrained in the wax can be economically recovered.

When hot carrier liquid is discharged with the wax, in accordance with the process of Patent 1,649,117, the carrier liquid must be' separated from the wax by somewhat elaborate procedure in accordance with the prior art before an at- 2 tempt is made to treat the wax to separate further oil therefrom. This procedure involves separating the bulk of the carrier liquid by gravity settling, and subsequent partial distillation to evaporate the last traces of carrier liquid. In case a procedure of this type is adopted, the Wax must also be diluted and rechilled to reprecipitate the wax prior to the second step of centrifugation to recover the entrained oil.

A particular object of the present invention consists in the provision of an economical procedure whereby the steps of gravity settling and partial distillation to remove carrier liquid from the wax discharged from the primary centrifuge may be avoided, and whereby a wax of high melting point may be produced as a separate byproduct in the practice of the invention.

Further objects and advantages of the invention and the manner in which they have been attained will be obvious after a reading of the following speciiication in the light of the attached flow sheet, in which the single ligure represents an illustrative embodiment of the practice of the invention.

Referring to the drawing by reference characters, a mixture of oil and wax, which has been diluted with naphtha and chilled to a temperature below 0cl F. to precipitate the wax after dilution, in accordance with the procedure described in Patents 1,351,265 and 1,649,117, referred to above, is passed to a centrifugal rotor I 0. A hot, aqueous carrier liquid is separately passed to the centrifugal rotor I0 adjacent the zone of discharge of Wax therefrom. A layer of aqueous carrier liquid occupies the zone adjacent the inner peripheral wall of the rotor I0 and prevents stickage of wax to the wall of the rotor andfacilitates the discharge of wax from the rotor. just as in the case of my prior Patent 1,649,117. Dewaxed oil solution is discharged as the lighter effluent from the centrifugal rotor, and a mixture of wax and the carrier liquid is separately discharged as the heavier effluent.

The mixture of wax and carrier liquid (which may be water or an aqueous salt solution) discharged from the rotor I0 is next mixed with a large quantity of a light hydrocarbon diluent, which may be the same diluent (naphtha) used in the primary centrifuging step performed in the rotor I 0. The amount of naphtha added at this stage of the process may be from 2% to 19 times as great as the quantity of wax phase discharged from the rotor I0. 'I'he mixture produced may. for example, contain of naphtha and 10% of the mixture of wax and oil discharged from the rotor I0. This mixture is next cooled to a temperature substantially higher than the freezing point of water.

If an attempt were made to cool the mixture to a point below the freezing point of the water which it contains, the formation of crystals of ice in the mixture would act as an impediment to subsequent centrifugal separation. If subsequent centrifugal separation were accomplished at a point below the freezing point of the water, the wax separated from this secondary centrifugal separating step would also be of relatively low melting point. l

A particular feature of the invention consists in the cooling of the mixture only to a point substantially above the freezing point of water at this stage of the process. By operating in this way. We obtain a wax effluent from the secondary centrifuging operation which is very valuable because of its high melting point, and we also separate water from the oil contained in the Wax eilluent of the centrifuge I0 in an economical manner.

In a preferred form of the invention, practiced when a separate wax fraction having a melting pint of approximately 160 F. is desired, the mixture of naphtha, wax and water formed by diluting with naphtha the wax and water eiliuent from the centrifuge I0 is passed to a cooler II, wherein its temperature is reduced to approximately 70 F. This entire mixture is then passed to a secondary centrifugal rotor I2. The water of the mixture, being the heaviest constituent, stratifies acacent the inner centrifugal wall of the rotor,'and the wax and a part of this water are discharged from the rotor together, the water acting as a carrier liquid in accordance with the process of Patent 1,351,265, to prevent adhesion of the wax to the Wall of the centrifugal rotor. At the relatively high temperature used in the secondary centrifuging operation, the low melting constituents of the wax are retained in solution in the oil and naphtha.

'I'his solution is separately discharged from the centrifuge I2 and is subjected to a further step of addition of naphtha, chilling and centrifugal separation to remove the wax from the oil and afford a further yield of oil of desirably low pour point. As illustrated in the flow sheet, the mixture of oil and wax, containing the major part of the naphtha introduced prior to the passage of the mixture to the cooler I I, is passed to a second cooler I3, which chills the solution to a temperature suiciently low to precipitate practically all of the wax from solution; e. g., to a temperature of 20 F.

The mixture of precipitated wax in the solution of oil in naphtha is passed from the cooler I3 to a third centrifugal separator I 4. A carrier liquid is separately passed to this third centrifugal separator, preferably in a heated condition, in accordance with Patent 1,649,117. The wax is discharged, together with the carrier liquid, from this third centrifugal, and the solution of oil in naphtha is separately discharged from this centrifugal as the lightest effluent. This oil solution discharged from centrifugal Il may be subjected to distillation to remove the diluent naphtha therefrom, but this solution can be most economically processed in accordance with the invention by employing it to dilute a fresh charge of oil to be dewaxed in the centrifuge I 0. The oil solution discharged from the centrifuge I4 is in a chilled condition, and is therefore particularly suitable for use in diluting the fresh charge of oil to be dewaxed. It also contains a very large proportion of naphtha (e. g., in case the naphtha added to the mixture of wax and water discharged from centrifuge I0 is added in a ratio to the wax eiliuent of approximately 9:1), and

`the presence of this high proportion of naphtha makes the oil eluent from centrifuge I4 a particularly desirable composition for dilution of a fresh charge of oil and wax.

While specific temperatures and specific proportions of diluents have been suggested above. it will be understood that these suggestions are made by way of illustration and not by way of limitation. Thus, the amount of naphtha added to the mixture of wax and water discharged from the centrifuge I0 may vary within fairly wide limits. Similarly, the temperature to which the mixture is chilled in the cooler II may be any temperature above the freezing point of water (or other aqueous carried liquid such as brine). In case it is desired to produce a wax effluent from the centrifuge I2 having a melting point of 150 F., for example, the mixture in the cooler Ii may be chilled to a temperature of 40 F. If, on the other hand, it is desired to produce a wax of extremely high melting point (e. g. 170 F.), the mixture may be cooled only to a temperature of F. The temperature to which the oil is chilled at this stage will, of course, determine the relative proportions and character of the wax which remains in solution and the wax which is precipitated respectively, and will accordingly determine the melting point of the wax discharged from the centrifuge I2.

Further modifications will be obvious to those skilled in the art, and I do not therefore wish to be limited except by the scope of the subjoined claims.

I claim:

1. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the wax in solution, but sufficiently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugalrotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, and discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor.

2. In the separation of wax and oil from each other, the processl comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor. feeding a hot aqueous carrier liquid of higher specific gravity than either the cil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, chilling the mixture so produced to a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the wax in solution, but .sufciently low to precipitate a higher melting part of the wax content of the mixture, passing the chilled mixture to a second centrifugal rotor, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, and discharg... ing wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor.

3. in the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, chilling the mixture so produced to a temperature between 40 and 100 F., passing the chilled mixture to a second centrifugal rotor, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, and discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor.

4. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor. discharging wax containing some entrained oil 'together with' said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sulficiently high to maintain a substantial part of the wax in solution but sufficiently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil. containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature sufficiently low to precipitate further wax therefrom, passing the mixture of oil and wax produced by said lastmentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor and separately discharging oil and wax from said third centrifugal rotor.

5. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some en-V trained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of Wax and carrier liquid discharged from said rotor, chilling the mixture so produced to a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the wax in solution, but sufciently low to precipitate a higher melting part of the wax content of the mixture, passing the chilled mixture to a second centrifugal rotor, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil Vdischarged from said second centrifugal rotor to a temperature sufficiently low to precipitate further wax therefrom, passing the mixture ofi-loll and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture tocentrifugal stratification in said third centrifugal rotor and separately discharging oil and wax from said third centrifugal rotor.

6. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixtureof waxand carrier liquid discharged from said rotor, chilling the mixture so produced to a temperature between 40 and 100 F., passing the chilled mixture to a second centrifugal rotor, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature suflciently low to precipitate further Wax therefrom, passing the mixture of oil and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor and separately discharging oil and wax from said third centrifugal rotor.

7. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor,

feeding a. hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufficiently high to m-aintain a substantial part of the wax in solution, but sufficiently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said centrifugal rotor to a temperature below 0 F. to precipitate further wax from solution, passing the mixture of oil and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor and separately discharging oil and wax from said third centrifugal rotor. 8. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said Wax to the mixture of wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and suffi ciently high to maintain a substantial part of the wax in solution, but sufficiently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor. discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature sumciently low to precipitate further wax therefrom, passing the mixture of oil and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor and separately discharging oil as the lighter phase from said third centrifugal rotor, and discharging wax together with carrier liquid separately added to said third centrifugal rotor as the heavier phase from said third centrifugal rotor.

9. In the separation of wax and oil from each other, the process comprising, feeding a. mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said Wax to the mixture of Wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the wax in solution, but suiciently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature sufficiently low to precipitate further wax therefrom, passing the mixture of oil and Wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor and separately discharging oil as the lighter phase from said third centrifugal rotor, and discharging Wax together with carrier liquid in a heated condition separately added to said third centrifugal rotor as the heavier phase from said third centrifugal rotor.

10. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated' wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said wax to the mixture of wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the Wax in solution, but sufiiciently low to maintain a higher melting part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the Wax in solution, as the lighter phase from said second centrifugal rotor, discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature sufficiently low to precipitate further wax therefrom, passing the mixture of oil and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor, separately discharging oil and wax from said third centrifugal rotor and diluting fresh stock to be dewaxed with the solution of oil in diluent discharged from said third centrifugal rotor. A

1l. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratication Within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, adding a diluent of lower specific gravity than said Wax to the mixture of Wax and carrier liquid discharged from said rotor, passing the mixture so produced to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufficiently high to maintain a substantial part of the wax in solution, but sufficiently low to maintain a higher melting part of the Wax content ofthe mixture in precipitated form, subjecting the mixture to centrifugal stratification in said second centrifugal rotor, discharging oil, containing a part of the Wax in solution, as the lighter phase from said second centrifugal rotor, discharging .wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor, chilling the solution of wax in oil discharged from said second centrifugal rotor to a temperature sufliciently low to precipitate further wax therefrom, passing the mixture of oil and wax produced by said last-mentioned chilling operation to a third centrifugal rotor, subjecting the mixture to centrifugal stratification in said third centrifugal rotor, separately discharging oil and wax from said third centrifugal rotor and diluting fresh stock to be dewaxed with the solution of oil in diluent discharged from said third centrifugal rotor while said solution of oil in diluent is still in a chilled condition.

l2. In the separation of wax and oil from each other, the process comprising, feeding a mixture of oil and precipitated wax to a centrifugal rotor, feeding a hot aqueous carrier liquid of higher specific gravity than either the oil or wax to said centrifugal rotor, subjecting the mixture to centrifugal stratification within said rotor, discharging oil as the lighter phase from said rotor, discharging wax containing some entrained oil together with said carrier liquid as the heavier phase from the rotor, passing the wax and carrier liquid discharged from said rotor, together with oil discharged with said wax from said rotor and sufficient diluent to render the oil phase lighter than the precipitated Wax, to a second centrifugal rotor at a temperature above the freezing point of the carrier liquid and sufliciently high to maintain a substantial part of the Wax in solution, but sufficiently low to maintain a higher melting `part of the wax content of the mixture in precipitated form, subjecting the mixture to centrifugal stratification in said -second centrifugal rotor, discharging oil containing a part of the wax in solution as the lighter phase from said second centrifugal rotor, and discharging wax of high melting point together with said carrier liquid as the heavier phase from said second centrifugal rotor. r

LEO D. JONES. 

